OCR Text |
Show 96 DR. GWYN JEFFREYS ON THE MOLLUSCA OF THE [Mar. 6, there are about 40 on the last whorl, some of them double ; the interstices are quite smooth : colour light yellowish-brown: spire raised : whorls 6, convex and rounded ; the last is equal to about two fifths of the spire ; apex twisted : suture distinct: mouth nearly circular; outer lip thin, but thicker and expanded at the base and partly folded over the umbilical perforation: umbilicus somewhat concave, with a small perforation. L. 0*15, B. 0*1. 'Porcupine' Exp. 1870: Atl. St. 16, 17«. Two specimens, one imperfect and the other not full-grown. 4. TROCHUS CANCELLATUS1, Jeffreys. (Plate XX. fig. 4.) S H E L L forming a depressed cone, rather thin, opaque, and lustreless: sculpture, oblique laminar ribs in the line of growth, which are crossed by as many but slighter spiral striae; there are about 20 ribs and striae on the last whorl; this sculpture covers the base, but the striae are wanting on the apex: colour pale yellowish-brown : spire rather depressed : whorls 5-6, convex; the last occupies three fifths of the shell; apex regular and compressed : mouth more round than oval, angulated above and below on the inner side : outer lip somewhat expanded and thickened : inner lip nearly straight, attached to the pillar below the periphery: umbilicus rather narrow, with a deep perforation which exposes the inner whorls. L. 0*1, B. 0*15. 'Porcupine' Exp. 1870 : Atl. St. 16. A single specimen. Distribution. Josephine Bank ('Josephine' Exp.); 340-430 fms. This and the following five species, or some of them, belong to tbe genus Macharoplax of Friele, which chiefly depends on the form of the radula or odontophore. 5. TROCHUS CINEREUS, Couthouy. Turbo cinereus, Couth, in Boston Journ. Nat. Hist. vol. ii. p. 99, pi. 3. f. 9 (1839). Trochus cinereus, B. C. iii. p. 304 ; v. p. 202. 'Porcupine' Exp. 1869: St. 14. A young and dead specimen, but apparently recent. Distribution. Arctic seas in both hemispheres, from Spitzbergen and Iceland to Floroe near Bergen and the Siberian coast, and from W . and E. Greenland to C. Cod, and Behring Str. to Sitka; 5-150 fms. Fossil. Post-tertiary: Scandinavia, Shetland, E.andW. Scotland, Ireland, N . America, and Sicily?; 0-460 ft. Margarita striata of Broderip and Sowerby (1828-29), but not Trochus striatus of Linn6, possibly M. arctica of Leach (1819) and T. leachii of Philippi, and M. sordida of Hancock. As fossil, perhaps T. granatelli of Calcara. Leach's description is indeterminable, viz.:-"M. purpurascente carnea tenuiter striolata, operculotestaceo." The animal has been described by me (in the 'Annals and Magazine of Nat. Hist.' for March 1877), and the odontophore by Friele. 1 Cross-barred. |